There are complex rules that procurement professionals working in the regulated procurement sectors (Public and Utilities sectors) have to follow and these rules have the force of law. There can be severe penalties for breaching the rules, so as well as seeking the best deal, there is an additional worry of ensuring compliance with the rules.
The rules governing regulated buyers are contained in 4 sets of procurement regulations covering the public sector and utilities sector. This is further complicated by having additional regulations covering concessions contracts and defence procurement.
The regulations take the form of Statutory Instruments (which therefore have the force of law), and breaching the rules set out in the regulations can be very costly as the courts can award damages in favour of disgruntled suppliers or even order that a procurement procedure is re-run.
Regulated procurement is a very complex area requiring detailed knowledge of the rules and procedures in order to minimise the risk of formal challenge for breaching the rules.